The present invention relates to a method and system for detecting the malfunction of a vehicle fuel level sensor. More particularly, the invention relates to a method and system that detects malfunctions more accurately by utilizing variation in the fuel level due to vehicle acceleration or deceleration.
A conventional method for detecting the malfunction of a vehicle fuel level sensor concludes that there is a fuel level sensor rationality malfunction if the fuel is within a certain range, the difference between maximum and minimum values of the fuel level sensor is below a certain value and if the vehicle has been travelling for a certain period of time. The conventional method also concludes that the fuel level sensor has malfunctioned and is stuck in a high or low state if the fuel is below the certain range, if the difference between maximum and minimum values of the fuel level sensor is below a certain value and if the vehicle has been travelling for a second certain period of time.
The conventional method uses fuel movement to test the fuel sensor. But, if the vehicle accelerates slowly and travels smoothly with a full fuel tank, the fuel level in the fuel tank may not show any change. Therefore, a conventional method may mistakenly conclude that a normally operating fuel level sensor is malfunctioning.
The present invention provides a fuel level sensor malfunction detecting method for a vehicle, in which change in the opening of the throttle valve is added as a malfunction judgment condition, or change in the opening of the throttle valve and a kick-down actuation are added as a malfunction judgment conditions, thereby making it possible to detect the fuel level sensor malfunctions more accurately.
In accordance with an embodiment of the present invention, a fuel level sensor malfunction detecting method for a vehicle includes: concluding certain monitoring conditions are satisfied; counting a time period during which a fuel level comes within a certain range and a difference between maximum and minimum values of the fuel level is less than a certain value; concluding a change rate of an opening of a throttle valve has shown a value greater than a certain value during the counted time period; accumulating malfunction occurrences if the change rate of the throttle valve opening was greater than the certain value; and concluding that the fuel level sensor has malfunctioned if the accumulated malfunction occurrences are greater than a certain malfunction value.
In another embodiment of the present invention a fuel level sensor malfunction detecting method for a vehicle includes: concluding certain monitoring conditions are satisfied; counting a time period during which a fuel level comes within a certain range and a difference between maximum and minimum values of the fuel level is less than a certain value; concluding a change rate of a throttle valve opening was greater than a certain value, and detecting a kick-down during the counted time period; accumulating malfunction occurrences if the change rate of the throttle valve opening was greater than the certain value, or if the kick-down was detected; and concluding that the fuel level sensor is malfunctioning if the accumulated malfunction occurrences are greater than a certain malfunction value.
In an additional embodiment of the present invention a method for detecting a failed fuel level sensor in a vehicle comprises: determining whether a fuel level sensor output is within a certain range; determining that a difference between a maximum and a minimum fuel level sensor output is below a certain value; monitoring the fuel level sensor and a throttle valve opening sensor for a time period wherein the vehicle is moving; accumulating a malfunction if, during the time period, the throttle valve opening sensor registered a rate of change greater than a certain rate; and concluding that the fuel level sensor is malfunctioning if the accumulated malfunctions exceed a certain malfunction value.
Furthermore, a system for detecting the malfunction of a fuel level sensor according to an embodiment of the invention includes a fuel level input, a throttle position input, a battery voltage input, a vehicle speed input, and an electronic control unit. In this embodiment the electronic control unit is programmed with instructions for concluding that the fuel level sensor is malfunctioning based on a throttle position. Another embodiment of the system of the invention includes a transmission signal input and the instructions further comprise concluding that the fuel level sensor is malfunctioning based on a transmission signal.